Using it for mountain biking in 35 degrees. Fits nicely under the helmet and actually improves the comfort of the helmet on the forehead. Gives me a full hour of sweat free sunglasses before getting saturated. A little warmer wearing it as it blocks some wind flow on the forehead but well worth it overall.
It works really well!
I feel that the headband could be tighter on the forehead. Perhaps different sizes should be available to accommodate various head sizes. I consider myself a heavy sweater and the headband seems to work fine for about 45 minutes of decent work. But then it seems like the seal gives way and the sweat starts dripping down at an accelerated rate. I would think that with a tighter fit this would not happen. I use the headband under a cycling helmet or under a running cap.
Before getting a haloheadband my eyes were red and burned from the sweat that would drip in my eye....now, I have no issues with that at all.
Halo II Pullover Headband